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Neuron DI for Java
There is a newer version: 6.7.1
/*
 * Copyright © 2016 Schlichtherle IT Services
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package global.namespace.neuron.di.internal;

import global.namespace.neuron.di.internal.proxy.Proxies;
import global.namespace.neuron.di.java.BreedingException;
import org.objectweb.asm.ClassReader;
import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.Opcodes;

import java.io.IOException;
import java.io.InputStream;
import java.lang.reflect.Method;
import java.util.List;
import java.util.stream.Stream;

import static global.namespace.neuron.di.internal.Reflection.defineSubclass;
import static java.util.Optional.ofNullable;
import static org.objectweb.asm.ClassReader.SKIP_DEBUG;
import static org.objectweb.asm.ClassWriter.COMPUTE_MAXS;
import static org.objectweb.asm.Type.getInternalName;

final class ASM implements Opcodes {

    private static final String PROXIES_PACKAGE_PREFIX = Proxies.PACKAGE_NAME + ".$";

    /**
     * Returns a class which proxies the given class or interface.
     */
    static  Class proxyClass(final Class clazz, final List bindableMethods) {
        final Class superclass;
        final Stream> streamOfInterfaces;
        if (clazz.isInterface()) {
            superclass = Object.class;
            streamOfInterfaces = Stream.concat(Stream.of(clazz), streamOfInterfaces(bindableMethods));
        } else {
            superclass = clazz;
            streamOfInterfaces = streamOfInterfaces(bindableMethods);
        }
        final Class[] arrayOfInterfaces = streamOfInterfaces.distinct().toArray(Class[]::new);
        final String proxyName = null != clazz.getClassLoader()
                ? clazz.getName().concat("$$proxy")
                : PROXIES_PACKAGE_PREFIX.concat(clazz.getName().replace('.', '$'));
        final ClassReader cr = classReader(clazz);
        final ClassWriter cw = new ClassWriter(cr, COMPUTE_MAXS);
        cr.accept(new ProxyClassVisitor(cw, internalName(proxyName), superclass, arrayOfInterfaces, bindableMethods), SKIP_DEBUG);
        return defineSubclass(clazz, proxyName, cw.toByteArray());
    }

    private static Stream> streamOfInterfaces(List bindableMethods) {
        return bindableMethods.stream().>map(Method::getDeclaringClass).filter(Class::isInterface);
    }

    private static ClassReader classReader(final Class clazz) {
        try (InputStream in = inputStream(clazz)) {
            return new ClassReader(in);
        } catch (IOException e) {
            throw new AssertionError(e);
        }
    }

    private static InputStream inputStream(final Class clazz) {
        final String resourceName = getInternalName(clazz).concat(".class");
        return ofNullable(clazz.getClassLoader())
                .map(cl -> cl.getResourceAsStream(resourceName))
                .orElseGet(() -> ofNullable(ClassLoader.getSystemResourceAsStream(resourceName))
                        .orElseThrow(() -> new BreedingException("Class not found: " + clazz.getName())));
    }

    private static String internalName(String className) {
        return className.replace('.', '/');
    }
}